For semiconductor radiation detectors, it is often desired to provide a position readout for detected radiation. Conventionally, position sensitivity can be provided by using a segmented electrode. However, such segmented electrodes can be disadvantageous in practice because they increase device complexity and create undesirable non-uniform electric fields within the detector.
FIG. 1 shows an example of this conventional approach. Here the body of the detector is referenced as 102, 104 is a p++ back side electrode and the n++ top electrode is segmented (i.e., electrodes 106a, 106b, and 106c) to provide position resolution. Electrical contact to the top electrodes can be made via aluminum contacts 108a, 108b, and 108c through insulator 110. Such contact is via AC coupling between the contacts and the corresponding electrode segments.
FIG. 2 shows typical electrical field modeling results for a configuration as in FIG. 1. It is apparent that the electric field is highly non-uniform. This has several drawbacks: (i) high field at the edge of the electrode can cause the detector to go into breakdown prematurely; (ii) the uneven electric field accelerates the charge carriers differently depending on their positions, producing very different signals as a function of the position of the impinging radiation (i.e., pulse time dispersion of collected charge); and (iii) the possibility of two adjacent readout electrodes becoming electrically connected due to radiation damage.
Accordingly, it would be an advance in the art to provide position sensitive radiation detectors that are free from such disadvantages.